The present invention relates to breathing devices and, more particularly, to breathing devices including protective masks for use in the presence of toxic or unpleasant airborne substances.
The possibility of encountering toxic or unpleasant airborne substances has led to the development of protective masks which filter or otherwise treat air before it is inhaled by the wearer. Such protective masks desirably have a number of attributes which are generally imperfectly achieved. A mask should interfere as little as possible with the wearer's activity, should have high adaptability to different wearers so that a small number of different sizes can fit an entire population, should be adaptable to all missions in which a wearer may be engaged, should be rapidly and easily donned and should provide positive and secure sealing to the user's body against the entry of the airborne substances.
Prior art protective masks fail in many of these categories and fail rather badly in some of these categories. Many prior art masks require four, five and more sizes to fit the entire user population. In addition, these masks significantly interfere with the wearer's vision, particularly a wearer who attempts to employ an optical apparatus such as binoculars or optical range finder. The rigid eyepieces of prior art protective masks space the eyepieces of the optical apparatus so far away from the wearer's eyes that the effective exit pupil of the optical apparatus is severely limited. In addition, prior art masks offer relatively poor downward vision.
Prior art masks require separate designs for each of a number of different missions. That is, a general purpose mask is not adaptable to vehicular applications and neither general purpose nor vehicular masks are suitable for aircrew applications. Furthermore, many prior art masks employ a single canister mounted on the side of the mask. Since the canister interferes with certain user activities such as, for example, firing a weapon, right-handed and left-handed masks are required which effectively doubles the inventory requirements.
Prior art masks are manufactured by molding a rubber face piece to which a lens system and other elements are attached at sealed seams. Besides increasing manufacturing cost due to the requirement for handling the large number of separate pieces, the prior art design poses a reliability problem since each of the seams presents a risk of seal failure thereby admitting the airborne substances which the mask is intended to exclude.
Prior art masks are molded in the folded condition. When such a mask must be donned, two hands are required to open it and to arrange the head straps prior to donning. These preliminary steps consume a number of seconds which may be critical in a close time situation.